K. Domen et al., OPTICAL GAIN FOR WURTZITE GAN WITH ANISOTROPIC STRAIN IN C-PLANE, IEEE journal of selected topics in quantum electronics, 3(2), 1997, pp. 450-455
We calculated band structures of (<1(1)over bar 00>)-oriented GaN with
various strains. We found that introducing anisotropic strain in the
c plane separates heavy hole and light hole bands, We also found that
a tensile strain in the (<1(1)over bar 00>) plane makes the light hole
band topmost. These two effects result in a reduction in the density
of states at the valence band edge. In this way, we can significantly
reduce the transparent carrier density to generate gain.